Sam Keeley Says It Was a 'Nightmare' Learning Philadelphia Accent for HBO's “Task” (Exclusive)

Sam Keeley is breaking down what it was for illustration to cleanable his Philadelphia accent for Task — and why nan process of getting it down was a "nightmare."

The Irish actor, 34, revealed to PEOPLE astatine nan New York City premiere of nan caller HBO bid connected Sept. 4 that nan accent — specifically, nan "Delco" dialect based successful Pennsylvania's Delaware County — was thing of an adjustment.

Taking spot successful Delaware County,Task stars Mark Ruffalo arsenic FBI supplier Tom Brandis and Keeley arsenic motorcycle pack personnel Jayson. As he shares, he had to get his "Delco" accent into bully shape arsenic he prepared for nan role. "It was a nightmare," he tells PEOPLE of learning nan accent pinch nan thief of dialect coach Susanne Sulby.

"She was responsible for maine being capable to sound nan measurement I sounded connected nan job," Keeley adds. "Because evidently nan Delco accent is very specific, you cognize what I mean? There's definite vowels. So for me, I had nary discourse to nan accent, I had nary discourse to nan language."

Keeley only started to consciousness "the cadence and nan rhythm" of nan Philly dialect erstwhile he sewage to nan city. He gives in installments to nan dialect coach, saying, "So it was Suzanne. She's fantastic."

Tom Pelphrey, who takes connected nan domiciled of Robbie Prendergast successful nan series, likewise revealed to TV Line that nan accent was a "great challenge."

"It was a small intimidating, but it was good. It kept maine very honest,” he said. “I had to activity really difficult astatine it. We had a awesome accent coach, Susanne Sulby… and ever had entree to her, which was amazing.”

Pelphrey, 43, added that he moreover made a friend pinch nan accent and was capable to prime up connected his vocal deliveries during telephone calls. "We’d talk astir shot and stuff, and he knew I was listening for his sounds a small bit, but we were comfortable capable pinch each different that he wasn’t excessively self-conscious,” Pelphrey said.

“Because there’s portion of an accent wherever you tin get it arsenic bully arsenic you want connected paper, but there’s a portion of my encephalon [where I] person to perceive nan existent point to spot that it sounds right.”

Task follows Ruffalo's Tom Brandis arsenic he investigates a drawstring of convulsive robberies successful nan Philadelphia suburbs. It besides features appearances from Emilia Jones, Jamie McShane,  Thuso Mbedu, Fabien Frankel, Alison Oliver and Raúl Castillo, among others. It premiered connected HBO connected Sept. 7, pinch caller episodes arriving weekly.

To hole for nan role, Ruffalo consulted pinch real-life retired FBI typical supplier Scott Duffey. As he told PEOPLE, Duffey taught him a meaningful instruction astir nan field: “I learned that nan champion FBI agents person a batch of empathy,” he said.

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Task airs play connected Sundays astatine 9 p.m. ET/PT connected HBO and is beryllium disposable to watercourse connected HBO Max.